|Articles about Biomaterials|
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| Sirolimus-eluting stents for treatment of complex bypass graft disease: insights from the SECURE registry
Costa, M., D. J. Angiolillo, et al. (2005), J Invasive Cardiol 17(8): 396-8.
Abstract: Graft disease remains a therapeutic challenge. Procedural complications and unsatisfactory patency rates are realized with both percutaneous intervention and repeat coronary artery bypass graft (CABG) surgery. The efficacy of sirolimus-eluting stents (SES) for the treatment of de novo coronary artery disease has been established, but the use of this technology to treat bypass graft disease remains undefined. The aim of this study was to evaluate the safety and feasibility of SES to treat patients with high-risk bypass graft disease. METHODS: The compassionate use of SES (SECURE) study included patients with recurrent coronary disease and no acceptable alternative available treatment, including brachytherapy or CABG. Outcomes from 76 patients (n = 94 lesions) with graft lesions treated with SES in the U.S. were compared with the outcomes of 176 patients (n = 311 lesions) with only native vessels. IVUS follow-up was performed at 8 months in 14 patients with graft SES treatment. RESULTS: In-hospital outcomes were similar between both groups, with 99% of patients discharged without adverse events. The incidence of target vessel failure including death, MI, and TVR at 12 months in the bypass graft group (55.3%) was similar to that observed in the native vessel group (45.5%, p = 0.17). Intimal hyperplasia (IH) measured by IVUS was 11.8 +/- 16.5%; 50% of patients with graft SES had < 1% IH at 8 months. CONCLUSION: Implantation of SES in high-risk patients with recurrent bypass graft disease is feasible. SES represents a future.
| Size and shape of biomaterial wear debris
Savio, J. A., 3rd, L. M. Overcamp, et al. (1994), Clin Mater 15(2): 101-47.
Abstract: A literature review of wear debris is presented. Included are debris retrieved at revision of total joint replacement and at autopsy, as well as debris produced in vitro in wear testers and joint simulators or otherwise fabricated for biological experiments. Observations of wear debris in vivo and in vitro are classified in tabular form according to material type, origin, size, shape and color. Polymer particles, most commonly ultra-high molecular weight polyethylene (UHMWPE), exhibit the largest size range and appear as granules, splinters or flakes, while ceramic particles possess the smallest size range and have a granular structure. Metal particles seen in vivo and in vitro, whether from cobalt-chromium alloys or, less frequently, other alloys, form granular or needle-like shapes and generally are smaller than polymer particles but larger than ceramic particles. Particles generated in joint simulators resemble the size and shape of in vivo wear particles from total joint replacement (TJR) retrieved at revision or autopsy. However, particles prepared in vitro, whether in simulators or by other means, do not consistently resemble wear debris particles from TJR.
| Size-controlled hydroxyapatite nanoparticles as self-organized organic-inorganic composite materials
Rusu, V. M., C. H. Ng, et al. (2005), Biomaterials 26(26): 5414-26.
Abstract: This paper presents some results concerning the size-controlled hydroxyapatite nanoparticles obtained in aqueous media in a biopolymer matrix from soluble precursors salts. Taking the inspiration from nature, where composite materials made of a polymer matrix and inorganic fillers are often found, e.g. bone, shell of crustaceans, shell of eggs, etc., the feasibility on making composite materials containing chitosan and nanosized hydroxyapatite was investigated. A stepwise co-precipitation approach was used to obtain different types of composites by means of different ratio between components. The synthesis of hydroxyapatite was carried out in the chitosan matrix from calcium chloride and sodium dihydrogenphosphate in alkaline solutions at moderate pH of 10-11 for 24 h. Our research is focused on studying and understanding the structure of this class of composites, aiming at the development of novel materials, controlled at the nanolevel scale. The X-ray diffraction technique was employed in order to study the kinetic of hydroxyapatite formation in the chitosan matrix as well as to determine the HAp crystallite sizes in the composite samples. The hydroxyapatite synthesized using this route was found to be nano-sized (15-50 nm). Moreover, applying an original approach to analyze the (002) XRD diffraction peak profile of hydroxyapatite by using a sum of two Gauss functions, the bimodal distribution of nanosized hydroxyapatite within the chitosan matrix was revealed. Two types of size distribution domains such as cluster-like (between 200 and 400 nm), which are the habitat of ''small'' hydroxyapatite nanocrystallites and scattered-like, which are the habitat of ''large'' hydroxyapatite nanocrystallites was probed by TEM and CSLM. The structural features of composites suggest that self-assembly processes might be involved. The composites contain nanosized hydroxyapatite with structural features close to those of biological apatites that make them attractive for bone tissue engineering applications.
| Size-controlled synthesis and optical properties of doped nanoparticles prepared by soft solution processing
Ullah, M. H. and C. S. Ha (2005), J Nanosci Nanotechnol 5(9): 1376-94.
Abstract: In this review, we outline the synthesis and luminescence properties of metal-ion-incorporated doped nanoparticles and surface-passivated doped nanoparticles. The synthetic routes we describe are limited to those involving soft solution processing. The doping effects are discussed in this review on the semiconductor nanoparticles confining the size range near to the 'quantum dot size.' The effects on luminescence with respect to ionic valance of dopants and the luminescence phenomena on mismatching of ionic radii between the host-guest are also provided. In addition, we discuss the role of passivated organic surfactants and the necessity of surface passivation of doped or undoped nanoparticles with other semiconductor materials that possess larger band gaps. Biocompatible semiconductor nanoparticles and some of their applications are also mentioned briefly.
| Sizing and tailoring the Dacron graft for reimplantation of the aortic valve
David, T. E. (2005), J Thorac Cardiovasc Surg 130(2): 243-4.
| Skin and mucosal testing of dental biomaterials
Wilson, J. (1980), Int Endod J 13(2): 112-5.
| Skin coverage with Biobrane biomaterial for the treatment of patients with toxic epidermal necrolysis
Arevalo, J. M. and J. A. Lorente (1999), J Burn Care Rehabil 20(5): 406-10.
Abstract: Toxic epidermal necrolysis (TEN) is an exfoliative skin disorder that may involve a large body surface area and mucosal surfaces. The microscopic changes that occur with this condition are similar to those that occur with superficial dermal burns, such as dermal detachment from the underlying dermis. Complications of TEN are related to the loss of the epithelial skin barrier and include pain, fluid and electrolyte loss, and an increased risk of sepsis. The treatment of a patient with TEN is best accomplished in a burn unit, where expert treatment of these complications can be provided. Medical treatment includes the administration of immunosuppressive therapy and the discontinuation of any previous corticosteroid treatment. Surgical management includes the debridement of necrotic areas. In this article, the surgical management of 8 consecutive patients with TEN who were admitted to the intensive care burn unit at the Hospital Universitario de Getafe in Madrid, Spain, from 1996 to 1998 is described. These patients were treated with extensive early debridement of necrotic skin areas followed by wound coverage with Biobrane (Dow B. Hickam, Inc, Sugarland, Tex), a temporary semisynthetic skin substitute. Skin coverage with this material decreases pain and fluid loss, and it possibly facilitates epithelization and decreases the risk of sepsis, without adverse side effects. This semisynthetic material meets some standards of an ideal skin substitute: it is easy to use, provides several beneficial physiologic effects, and improves patients' comfort. In the 8 cases of patients with TEN that were studied, the use of Biobrane skin substitute for the coverage of massive areas of detached skin was found to be an important aspect of treatment.
| Slow crack growth behaviour of hydroxyapatite ceramics
Benaqqa, C., J. Chevalier, et al. (2005), Biomaterials 26(31): 6106-12.
Abstract: Among materials for medical applications, hydroxyapatite is one of the best candidates in orthopedics, since it exhibits a composition similar to the mineral part of bone. Double torsion technique was here performed to investigate slow crack growth behaviour of dense hydroxyapatite materials. Crack rate, V, versus stress intensity factor, K(I), laws were obtained for different environments and processing conditions. Stress assisted corrosion by water molecules in oxide ceramics is generally responsible for slow crack growth. The different propagation stages obtained here could be analyzed in relation to this process. The presence of a threshold defining a safety range of use was also observed. Hydroxyapatite ceramics appear to be very sensitive to slow crack growth, crack propagation occurring even at very low K(I). This can be explained by the fact that they contain hydroxyl groups (HAP: Ca(10)(PO(4))(6)(OH)(2)), favouring water adsorption on the crack surface and thus a strong decrease of surface energy in the presence of water. This study demonstrates that processing conditions must be carefully controlled, specially sintering temperature, which plays a key role on V-K(I) laws. Sintering at 50 degrees C above or below the optimal temperature, for example, may shift the V-K(I) law towards very low stress intensity factors. The influence of ageing is finally discussed.
| Small diamines as modifiers for phosphatidylcholine/phosphatidylserine coatings in capillary electrochromatography
Varjo, S. J., J. T. Hautala, et al. (2005), J Chromatogr A 1081(1): 92-8.
Abstract: Greater stability of liposome coatings and improved resolution of model steroids in capillary electrochromatography (CEC) were sought by adding small diamines (ethylenediamine, diaminopropane, bis-tris-propane, or N-(2-hydroxyethyl)piperazine-N'-(2-ethanesulfonic acid, HEPES)) to the liposome solution before coating of fused silica capillaries. The phospholipid coatings consisted of 1 mM of 8:2 mol% phosphatidylcholine (PC)/phosphatidylserine (PS) and 5 mM of modifier in buffer solutions (acetate, phosphate, or Tris) at pH 4.0-7.4. The coating was based on a published procedure, and five steroids were used as neutral model analytes in evaluation of the coating. The results showed that under optimal conditions, the small linear diamines increased the packing density of anionic phospholipids, leading to improved separations. In addition, the choice of buffer for the liposome coating and separation appeared to influence the performance of the coatings. While buffers with amino groups take part in the phospholipid bilayer formation, buffers like phosphate may even have negative effect on coating formation. The factors affecting phospholipid coatings with diamines as modifiers are clarified.
| Small molecule microarrays: from proteins to mammalian cells - are we there yet?
Chiosis, G. and J. L. Brodsky (2005), Trends Biotechnol 23(6): 271-4.
Abstract: A recent publication by Stockwell and colleagues documents a leap forward toward the continued development of small molecule microarray (SMM) technology. By creating microarrays of small molecules impregnated in a biodegradable polymer, the authors have, for the first time, shown that SMMs can be used in a cell-based format. This technological improvement opens the door for using SMMs to perform high-throughput screens in mammalian cells.
| Smart and genetically engineered biomaterials and drug delivery systems
Kopecek, J. (2003), Eur J Pharm Sci 20(1): 1-16.
Abstract: The design, synthesis, and properties of novel stimuli-sensitive and genetically engineered biomaterials and drug delivery systems are reviewed. Two approaches to their engineering are presented. One approach is to improve the traditional methods of synthesis, as demonstrated by the example of controlled copolymerization of alpha-amino acid N-carboxyanhydrides. The other approach, discussed in more detail, uses genetic engineering methods. The design of hybrid hydrogel systems whose components derive from at least two distinct classes of molecules, e.g., synthetic macromolecules and protein domains, is assessed. The design of self-assembling block copolymers is discussed in detail. Finally, the pharmaceutics related applications of these materials are presented.
| 'Smart' delivery systems for biomolecular therapeutics
Stayton, P. S., M. E. El-Sayed, et al. (2005), Orthod Craniofac Res 8(3): 219-25.
Abstract: OBJECTIVE: There is a strong need for drug delivery systems that can deliver biological signals from biomaterials and tissue engineering scaffolds, and a particular need for new delivery systems that can efficiently deliver biomolecules to intracellular targets. Viruses and pathogens have evolved potent molecular machinery that sense the lowered pH gradient of the endosomal compartment and become activated to destabilize the endosomal membrane, thereby enhancing protein or DNA transport to the cytoplasmic compartment. A key feature of many of these biological delivery systems is that they are reversible, so that the delivery systems are not directly toxic. These delivery systems have the ability to change their structural and functional properties and thus display remarkable 'smart' material properties. The objective of this presentation is to review the initial development of smart polymeric carriers that mimic these biological delivery systems and combine similar pH-sensitive, membrane-destabilizing activity for the delivery of therapeutic biomolecules. DESIGN: We have developed new 'smart' polymeric carriers to more effectively deliver and broaden the available types of biomolecular therapeutics. The polymers are hydrophilic and stealth-like at physiological pH, but become membrane-destabilizing after uptake into the endosomal compartment where they enhance the release of therapeutic cargo into the cytoplasm. They can be designed to provide a range of pH profiles and membrane-destabilizing activities, allowing their molecular properties to be matched to specific drugs and loading ranges. A versatile set of linker chemistries is available to provide degradable conjugation sites for proteins, nucleic acids, and/or targeting moieties. RESULTS: The physical properties of several pH-responsive polymers were examined. The activity and pH profile can be manipulated by controlling the length of hydrophobic alkyl segments. The delivery of poly(propyl acrylic acid) (PPAA)-containing lipoplexes significantly enhanced wound healing through the interconnected effects of altered extracellular matrix organization and greater vascularization. PPAA has also been shown to enhance cytoplasmic delivery of a model protein therapeutic. Polymeric carriers displaying pH-sensitive, membrane-destabilizing activity were also examined. The pH profile is controlled by the choice of the alkylacrylic acid monomer and by the ratio of the carboxylate-containing alkylacrylic acid monomer to alkylacrylate monomer. The membrane destabilizing activity is controlled by the lengths of the alkyl segment on the alkylacrylic acid monomer and the alkylacrylate monomer, as well as by their ratio in the final polymer chains. CONCLUSION: The molecular mechanisms that proteins use to sense and destabilize provide interesting paradigms for the development of new polymeric delivery systems that mimic biological strategies for promoting the intracellular delivery of biomolecular drugs. The key feature of these polymers is their ability to directly enhance the intracellular delivery of proteins and DNA, by destabilizing biological membranes in response to vesicular compartment pH changes. The ability to deliver a wide variety of protein and nucleic acid drugs to intracellular compartments from tissue engineering and regenerative scaffolds could greatly enhance control of important processes such as inflammation, angiogenesis, and biomineralization.
| Smart implant materials
Lendlein, A., K. Kratz, et al. (2005), Med Device Technol 16(3): 12-4.
Abstract: The combination of stimuli-sensitive implant materials and minimally invasive surgery techniques is expected to give rise to numerous applications. Biodegradable thermoplastic elastomers are presented here as an example of a group of biodegradable implant materials with shape-memory properties. Their capabilities and use in a smart suture are described.
| Snowflake opacification of poly(methyl methacrylate) intraocular lens optic biomaterial: a newly described syndrome
Peng, Q., D. J. Apple, et al. (2001), Int Ophthalmol Clin 41(3): 91-107.
| Society of Biomaterials Graduate Degree Candidate Student Research Award. Matrix metalloproteinase inhibitor within an absorbable coating for vascular applications: delivery device characterization and reduction of smooth muscle cell proliferation and migration
Caldwell, R. A., N. Vyavahare, et al. (2003), J Biomed Mater Res A 67(1): 1-10.
Abstract: Significant occurrences of arterial restenosis remain a complicating factor of endovascular stent implantation. The incorporation of GM6001, a matrix metalloproteinase inhibitor (MMPI), into a poly(lactide-co-glycolide) (PLGA) absorbable coating for 316L stainless steel is proposed as a means to reduce the rate of smooth muscle cell proliferation and migration. Coatings were fabricated using a solvent evaporation technique, and the surfaces were characterized by noncontacting profilometry and scanning electron microscopy. Sufficient degradation of the PLGA determined by gel permeation chromatography occurred to release adequate amounts of the GM6001 from the coating within a 7-day period. A cumulative GM6001 release at day 42 was determined to be 77.8 +/- 1.4% of the actual GM6001 content within the coating. The coating containing the GM6001 reduced the rate of in vitro cell growth of human aortic smooth muscle cell (HASMC) by 30.7 and 37.4% compared to the metallic substrate only after 4 and 7 days, respectively. However, the MMP-2 activity normalized to cell number was not statistically different between the GM6001 releasing coating and the metal substrate. Using a scrape wound injury assay, the migration of HASMCs was shown to be decreased by 21.4% with GM6001 released from the PLGA coating compared to metallic substrate only. These results suggest that releasing a MMPI from an absorbable coating of a metallic substrate provides a reduction of HASMC proliferation and migration rates, while preserving the overall MMP activity in efforts to retain normal cellular regulation.
| Sodium alginate as a novel therapeutic option in experimental colitis
Mirshafiey, A., A. Khodadadi, et al. (2005), Scand J Immunol 61(4): 316-21.
Abstract: The potential therapeutic effect of low-viscosity sodium alginate (LVA) was studied in a rat model of acute colitis induced by intracolonic administration of acetic acid. This experimental model produced a significant ulcerative colitis. Induction of colitis also significantly enhanced the serum and colonic mucosal cytokine (IL-6 and TNF-alpha) and eicosanoid (LTB4 and PGE2) levels, which paralleled with the severity of colitis. LVA solution was administered orally as drinking water at concentration of 0.5% (W/V) for 1 week. The tolerability and inhibitory effect of LVA on matrix metalloproteinase-2 (MMP-2) were tested using WEHI-164 cell line and zymography method. The results showed that LVA therapy is able to significantly reduce colonic damage score, histological lesion, serum and colonic mucosal IL-6, TNF-alpha, LTB4 and PGE2 levels in treated group compared with nontreated controls. Moreover, in vitro examinations revealed that treatment with LVA could diminish MMP-2 activity. It is concluded that LVA is able to suppress acetic acid-induced colitis in rats. Some of the action of LVA may be associated with its inhibitory effects on cytokine and eicosanoid production and MMP-2 activity. Our data suggest that LVA could potentially be a novel therapeutic option for inflammatory bowel disease.
| Soft tissue fillers for management of the aging perioral complex
Sclafani, A. P. (2005), Facial Plast Surg 21(1): 74-8.
Abstract: Rejuvenative therapy of the lower face has traditionally been surgical in nature, with office-based treatments such as soft tissue fillers relegated to "second tier" status. However, traditional rhytidectomy does not significantly affect the perioral complex and leaves the central lower face unaltered and unimproved. If it is left untreated, there is a clear disparity between the rejuvenated neck and aged perioral area. Soft tissue augmentation of the perioral area can provide rapid aesthetic improvement. Careful analysis of this area and appropriate treatment can harmonize these areas and produce a globally aesthetic result.
| Soft tissue implants and fillers
Owens, J. M. (2005), Otolaryngol Clin North Am 38(2): 361-9.
Abstract: The number and variety of soft tissue implants and fillers at the clinician's disposal continues to increase rapidly as new materials and bioengineering techniques evolve. The ideal implant for all purposes does not yet exist, so the clinician must be familiar with a wide variety of products for each application. Continued advances in synthetic, allogeneic, and autologous products and experience with existing products will further augment the surgeon's armamentarium in the coming years.
| Soft tissue response to four dense ceramic materials and two clinically used biomaterials
Richardson, W. C., Jr., J. J. Klawitter, et al. (1975), J Biomed Mater Res 9(4): 73-80.
Abstract: Disk-shaped implants of spinel, alumina, mullite, zircon, a cast Co-Cr-Mo alloy, and ultra-high molecular weight polyethylene (UHMWPE), were implanted in the paraspinalis muscle of 12 adult, male, white New Zealand rabbits. Prior to implantation the implants were characterized with respect to size and shape, weight and surface roughness. After periods of 1 month, 2 months, and 4 months, the rabbits were sacrificed and the tissue specimens were retrieved with the implants still intact. Histological examination of the tissues surrounding the implants along with changes in the size and shape, weight, and surface roughness of the implants were used as criteria for evaluating these materials for implant purposes. No surfaces degradation of any of the materials was detected using scanning electron microscopy. Fibrous tissue seemed to adhere to the UHMWPE implants more than any other material used in this study. Large amounts of fibrous tissue were also found to adhere to the cast Co-Cr-Mo alloy implants. The histological results indicated that within the limits of this investigation, the biocompatibility of the ceramic materials used in this study compared favorably with the clinically used Co-Cr-Mo alloy implants and the UHMWPE implants.
| Soft-tissue response to synthetic biomaterials
Morehead, J. M. and G. R. Holt (1994), Otolaryngol Clin North Am 27(1): 195-201.
Abstract: The soft-tissue response to an implanted synthetic material is an inflammatory reaction to foreign body; factors that minimize this inflammation will maximize biocompatibility. The ideal implant is selected from a material that is non-toxic, nonantigenic and in chemical proximity to calcium or carbon on the periodic table. If it is porous, the pores should be large enough to admit immune and phagocytic cells and ideally, to allow native tissue ingrowth. The implant should be of appropriate size and shape and should be implanted in the correct location. The material should be nonparticulate, should resist fragmentation, and should be secured in the selected location after gentle insertion. All these factors help decrease the body's natural response to an implanted foreign body, but inflammation and foreign body reaction are the common threads in all responses to all implanted synthetic materials. Optimum soft-tissue biocompatibility, characterized either by thin fibrous encapsulation or by mesenchymal ingrowth into pores and interstices, is achieved by avoiding or containing this response.
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